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<a class="jxr_linenumber" name="1" href="#1">1</a>   <strong class="jxr_keyword">package</strong> net.big_oh.common.utils;
<a class="jxr_linenumber" name="2" href="#2">2</a>   
<a class="jxr_linenumber" name="3" href="#3">3</a>   <em class="jxr_comment">/*</em>
<a class="jxr_linenumber" name="4" href="#4">4</a>   <em class="jxr_comment"> Copyright (c) 2008 Dave Wingate dba Big-Oh Software (www.big-oh.net)</em>
<a class="jxr_linenumber" name="5" href="#5">5</a>   
<a class="jxr_linenumber" name="6" href="#6">6</a>   <em class="jxr_comment"> Permission is hereby granted, free of charge, to any person</em>
<a class="jxr_linenumber" name="7" href="#7">7</a>   <em class="jxr_comment"> obtaining a copy of this software and associated documentation</em>
<a class="jxr_linenumber" name="8" href="#8">8</a>   <em class="jxr_comment"> files (the "Software"), to deal in the Software without</em>
<a class="jxr_linenumber" name="9" href="#9">9</a>   <em class="jxr_comment"> restriction, including without limitation the rights to use,</em>
<a class="jxr_linenumber" name="10" href="#10">10</a>  <em class="jxr_comment"> copy, modify, merge, publish, distribute, sublicense, and/or sell</em>
<a class="jxr_linenumber" name="11" href="#11">11</a>  <em class="jxr_comment"> copies of the Software, and to permit persons to whom the</em>
<a class="jxr_linenumber" name="12" href="#12">12</a>  <em class="jxr_comment"> Software is furnished to do so, subject to the following</em>
<a class="jxr_linenumber" name="13" href="#13">13</a>  <em class="jxr_comment"> conditions:</em>
<a class="jxr_linenumber" name="14" href="#14">14</a>  
<a class="jxr_linenumber" name="15" href="#15">15</a>  <em class="jxr_comment"> The above copyright notice and this permission notice shall be</em>
<a class="jxr_linenumber" name="16" href="#16">16</a>  <em class="jxr_comment"> included in all copies or substantial portions of the Software.</em>
<a class="jxr_linenumber" name="17" href="#17">17</a>  
<a class="jxr_linenumber" name="18" href="#18">18</a>  <em class="jxr_comment"> THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,</em>
<a class="jxr_linenumber" name="19" href="#19">19</a>  <em class="jxr_comment"> EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES</em>
<a class="jxr_linenumber" name="20" href="#20">20</a>  <em class="jxr_comment"> OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND</em>
<a class="jxr_linenumber" name="21" href="#21">21</a>  <em class="jxr_comment"> NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT</em>
<a class="jxr_linenumber" name="22" href="#22">22</a>  <em class="jxr_comment"> HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,</em>
<a class="jxr_linenumber" name="23" href="#23">23</a>  <em class="jxr_comment"> WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING</em>
<a class="jxr_linenumber" name="24" href="#24">24</a>  <em class="jxr_comment"> FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR</em>
<a class="jxr_linenumber" name="25" href="#25">25</a>  <em class="jxr_comment"> OTHER DEALINGS IN THE SOFTWARE.</em>
<a class="jxr_linenumber" name="26" href="#26">26</a>  <em class="jxr_comment"> */</em>
<a class="jxr_linenumber" name="27" href="#27">27</a>  
<a class="jxr_linenumber" name="28" href="#28">28</a>  <strong class="jxr_keyword">import</strong> java.math.BigInteger;
<a class="jxr_linenumber" name="29" href="#29">29</a>  <strong class="jxr_keyword">import</strong> java.util.ArrayList;
<a class="jxr_linenumber" name="30" href="#30">30</a>  <strong class="jxr_keyword">import</strong> java.util.Collection;
<a class="jxr_linenumber" name="31" href="#31">31</a>  <strong class="jxr_keyword">import</strong> java.util.Enumeration;
<a class="jxr_linenumber" name="32" href="#32">32</a>  <strong class="jxr_keyword">import</strong> java.util.HashSet;
<a class="jxr_linenumber" name="33" href="#33">33</a>  <strong class="jxr_keyword">import</strong> java.util.Iterator;
<a class="jxr_linenumber" name="34" href="#34">34</a>  <strong class="jxr_keyword">import</strong> java.util.List;
<a class="jxr_linenumber" name="35" href="#35">35</a>  <strong class="jxr_keyword">import</strong> java.util.Set;
<a class="jxr_linenumber" name="36" href="#36">36</a>  
<a class="jxr_linenumber" name="37" href="#37">37</a>  <strong class="jxr_keyword">import</strong> org.apache.commons.collections.CollectionUtils;
<a class="jxr_linenumber" name="38" href="#38">38</a>  
<a class="jxr_linenumber" name="39" href="#39">39</a>  <em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="40" href="#40">40</a>  <em class="jxr_javadoccomment"> * A set of static convenience methods for working with collections.</em>
<a class="jxr_linenumber" name="41" href="#41">41</a>  <em class="jxr_javadoccomment"> * </em>
<a class="jxr_linenumber" name="42" href="#42">42</a>  <em class="jxr_javadoccomment"> * @author davewingate</em>
<a class="jxr_linenumber" name="43" href="#43">43</a>  <em class="jxr_javadoccomment"> * </em>
<a class="jxr_linenumber" name="44" href="#44">44</a>  <em class="jxr_javadoccomment"> */</em>
<a class="jxr_linenumber" name="45" href="#45">45</a>  <strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">class</strong> <a href="../../../../net/big_oh/common/utils/CollectionsUtil.html">CollectionsUtil</a>
<a class="jxr_linenumber" name="46" href="#46">46</a>  {
<a class="jxr_linenumber" name="47" href="#47">47</a>  
<a class="jxr_linenumber" name="48" href="#48">48</a>  	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="49" href="#49">49</a>  <em class="jxr_javadoccomment">	 * Constructs a single String by iterating over the elements in the</em>
<a class="jxr_linenumber" name="50" href="#50">50</a>  <em class="jxr_javadoccomment">	 * collection parameter, calling toString() on each method.</em>
<a class="jxr_linenumber" name="51" href="#51">51</a>  <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="52" href="#52">52</a>  <em class="jxr_javadoccomment">	 * @param &lt;T&gt;</em>
<a class="jxr_linenumber" name="53" href="#53">53</a>  <em class="jxr_javadoccomment">	 * @param collection</em>
<a class="jxr_linenumber" name="54" href="#54">54</a>  <em class="jxr_javadoccomment">	 * @return A comma-separated value String.</em>
<a class="jxr_linenumber" name="55" href="#55">55</a>  <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="56" href="#56">56</a>  	<strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">static</strong> &lt;T <strong class="jxr_keyword">extends</strong> Object&gt; String toCsvString(Collection&lt;T&gt; collection)
<a class="jxr_linenumber" name="57" href="#57">57</a>  	{
<a class="jxr_linenumber" name="58" href="#58">58</a>  		<strong class="jxr_keyword">return</strong> toXsvString(collection, <span class="jxr_string">", "</span>);
<a class="jxr_linenumber" name="59" href="#59">59</a>  	}
<a class="jxr_linenumber" name="60" href="#60">60</a>  
<a class="jxr_linenumber" name="61" href="#61">61</a>  	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="62" href="#62">62</a>  <em class="jxr_javadoccomment">	 * Constructs a single String by iterating over the elements in the</em>
<a class="jxr_linenumber" name="63" href="#63">63</a>  <em class="jxr_javadoccomment">	 * collection parameter, calling toString() on each method.</em>
<a class="jxr_linenumber" name="64" href="#64">64</a>  <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="65" href="#65">65</a>  <em class="jxr_javadoccomment">	 * @param &lt;T&gt;</em>
<a class="jxr_linenumber" name="66" href="#66">66</a>  <em class="jxr_javadoccomment">	 * @param collection</em>
<a class="jxr_linenumber" name="67" href="#67">67</a>  <em class="jxr_javadoccomment">	 * @param separator</em>
<a class="jxr_linenumber" name="68" href="#68">68</a>  <em class="jxr_javadoccomment">	 * @return A separator-separated value String.</em>
<a class="jxr_linenumber" name="69" href="#69">69</a>  <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="70" href="#70">70</a>  	<strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">static</strong> &lt;T <strong class="jxr_keyword">extends</strong> Object&gt; String toXsvString(Collection&lt;T&gt; collection, String separator)
<a class="jxr_linenumber" name="71" href="#71">71</a>  	{
<a class="jxr_linenumber" name="72" href="#72">72</a>  		<strong class="jxr_keyword">if</strong> (collection == <strong class="jxr_keyword">null</strong>)
<a class="jxr_linenumber" name="73" href="#73">73</a>  		{
<a class="jxr_linenumber" name="74" href="#74">74</a>  			<strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="75" href="#75">75</a>  		}
<a class="jxr_linenumber" name="76" href="#76">76</a>  
<a class="jxr_linenumber" name="77" href="#77">77</a>  		StringBuffer sb = <strong class="jxr_keyword">new</strong> StringBuffer();
<a class="jxr_linenumber" name="78" href="#78">78</a>  
<a class="jxr_linenumber" name="79" href="#79">79</a>  		<strong class="jxr_keyword">int</strong> count = 0;
<a class="jxr_linenumber" name="80" href="#80">80</a>  		<strong class="jxr_keyword">for</strong> (Iterator&lt;T&gt; iter = collection.iterator(); iter.hasNext(); count++)
<a class="jxr_linenumber" name="81" href="#81">81</a>  		{
<a class="jxr_linenumber" name="82" href="#82">82</a>  			<strong class="jxr_keyword">if</strong> (count &gt; 0)
<a class="jxr_linenumber" name="83" href="#83">83</a>  			{
<a class="jxr_linenumber" name="84" href="#84">84</a>  				sb.append(separator);
<a class="jxr_linenumber" name="85" href="#85">85</a>  			}
<a class="jxr_linenumber" name="86" href="#86">86</a>  			sb.append(iter.next().toString());
<a class="jxr_linenumber" name="87" href="#87">87</a>  		}
<a class="jxr_linenumber" name="88" href="#88">88</a>  
<a class="jxr_linenumber" name="89" href="#89">89</a>  		<strong class="jxr_keyword">return</strong> sb.toString();
<a class="jxr_linenumber" name="90" href="#90">90</a>  	}
<a class="jxr_linenumber" name="91" href="#91">91</a>  
<a class="jxr_linenumber" name="92" href="#92">92</a>  	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="93" href="#93">93</a>  <em class="jxr_javadoccomment">	 * Wraps an {@link Enumeration} as an instance of {@link Iterable} so that</em>
<a class="jxr_linenumber" name="94" href="#94">94</a>  <em class="jxr_javadoccomment">	 * it can be passed into a "for each" logical construct.</em>
<a class="jxr_linenumber" name="95" href="#95">95</a>  <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="96" href="#96">96</a>  <em class="jxr_javadoccomment">	 * @param &lt;T&gt;</em>
<a class="jxr_linenumber" name="97" href="#97">97</a>  <em class="jxr_javadoccomment">	 * @param enumeration</em>
<a class="jxr_linenumber" name="98" href="#98">98</a>  <em class="jxr_javadoccomment">	 * @return An Iterable representation of the enumeration parameter.</em>
<a class="jxr_linenumber" name="99" href="#99">99</a>  <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="100" href="#100">100</a> 	<strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">static</strong> &lt;T&gt; Iterable&lt;T&gt; toIterable(<strong class="jxr_keyword">final</strong> Enumeration&lt;T&gt; enumeration)
<a class="jxr_linenumber" name="101" href="#101">101</a> 	{
<a class="jxr_linenumber" name="102" href="#102">102</a> 
<a class="jxr_linenumber" name="103" href="#103">103</a> 		<strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">new</strong> Iterable&lt;T&gt;()
<a class="jxr_linenumber" name="104" href="#104">104</a> 		{
<a class="jxr_linenumber" name="105" href="#105">105</a> 			<strong class="jxr_keyword">public</strong> Iterator&lt;T&gt; iterator()
<a class="jxr_linenumber" name="106" href="#106">106</a> 			{
<a class="jxr_linenumber" name="107" href="#107">107</a> 				<strong class="jxr_keyword">return</strong> <strong class="jxr_keyword">new</strong> Iterator&lt;T&gt;()
<a class="jxr_linenumber" name="108" href="#108">108</a> 				{
<a class="jxr_linenumber" name="109" href="#109">109</a> 
<a class="jxr_linenumber" name="110" href="#110">110</a> 					<strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">boolean</strong> hasNext()
<a class="jxr_linenumber" name="111" href="#111">111</a> 					{
<a class="jxr_linenumber" name="112" href="#112">112</a> 						<strong class="jxr_keyword">return</strong> enumeration.hasMoreElements();
<a class="jxr_linenumber" name="113" href="#113">113</a> 					}
<a class="jxr_linenumber" name="114" href="#114">114</a> 
<a class="jxr_linenumber" name="115" href="#115">115</a> 					<strong class="jxr_keyword">public</strong> T next()
<a class="jxr_linenumber" name="116" href="#116">116</a> 					{
<a class="jxr_linenumber" name="117" href="#117">117</a> 						<strong class="jxr_keyword">return</strong> enumeration.nextElement();
<a class="jxr_linenumber" name="118" href="#118">118</a> 					}
<a class="jxr_linenumber" name="119" href="#119">119</a> 
<a class="jxr_linenumber" name="120" href="#120">120</a> 					<strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">void</strong> remove()
<a class="jxr_linenumber" name="121" href="#121">121</a> 					{
<a class="jxr_linenumber" name="122" href="#122">122</a> 						<strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> UnsupportedOperationException();
<a class="jxr_linenumber" name="123" href="#123">123</a> 					}
<a class="jxr_linenumber" name="124" href="#124">124</a> 				};
<a class="jxr_linenumber" name="125" href="#125">125</a> 
<a class="jxr_linenumber" name="126" href="#126">126</a> 			}
<a class="jxr_linenumber" name="127" href="#127">127</a> 		};
<a class="jxr_linenumber" name="128" href="#128">128</a> 
<a class="jxr_linenumber" name="129" href="#129">129</a> 	}
<a class="jxr_linenumber" name="130" href="#130">130</a> 
<a class="jxr_linenumber" name="131" href="#131">131</a> 	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="132" href="#132">132</a> <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="133" href="#133">133</a> <em class="jxr_javadoccomment">	 * @param &lt;T&gt;</em>
<a class="jxr_linenumber" name="134" href="#134">134</a> <em class="jxr_javadoccomment">	 * @param originalSet</em>
<a class="jxr_linenumber" name="135" href="#135">135</a> <em class="jxr_javadoccomment">	 *            The set of original objects from which combinations of size k</em>
<a class="jxr_linenumber" name="136" href="#136">136</a> <em class="jxr_javadoccomment">	 *            would be generated.</em>
<a class="jxr_linenumber" name="137" href="#137">137</a> <em class="jxr_javadoccomment">	 * @param k</em>
<a class="jxr_linenumber" name="138" href="#138">138</a> <em class="jxr_javadoccomment">	 *            The size of combinations that would be generated.</em>
<a class="jxr_linenumber" name="139" href="#139">139</a> <em class="jxr_javadoccomment">	 * @return Returns the number of possible ways to construct subsets of size</em>
<a class="jxr_linenumber" name="140" href="#140">140</a> <em class="jxr_javadoccomment">	 *         k from the originalSet.</em>
<a class="jxr_linenumber" name="141" href="#141">141</a> <em class="jxr_javadoccomment">	 * @throws IllegalArgumentException</em>
<a class="jxr_linenumber" name="142" href="#142">142</a> <em class="jxr_javadoccomment">	 *             thrown if k is less than zero of greater than the size of the</em>
<a class="jxr_linenumber" name="143" href="#143">143</a> <em class="jxr_javadoccomment">	 *             original set.</em>
<a class="jxr_linenumber" name="144" href="#144">144</a> <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="145" href="#145">145</a> 	<strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">static</strong> &lt;T&gt; BigInteger countCombinations(Set&lt;T&gt; originalSet, <strong class="jxr_keyword">int</strong> k) <strong class="jxr_keyword">throws</strong> IllegalArgumentException
<a class="jxr_linenumber" name="146" href="#146">146</a> 	{
<a class="jxr_linenumber" name="147" href="#147">147</a> 		<strong class="jxr_keyword">return</strong> countCombinations(originalSet.size(), k);
<a class="jxr_linenumber" name="148" href="#148">148</a> 	}
<a class="jxr_linenumber" name="149" href="#149">149</a> 
<a class="jxr_linenumber" name="150" href="#150">150</a> 	<strong class="jxr_keyword">protected</strong> <strong class="jxr_keyword">static</strong> &lt;T&gt; BigInteger countCombinations(<strong class="jxr_keyword">int</strong> n, <strong class="jxr_keyword">int</strong> k) <strong class="jxr_keyword">throws</strong> IllegalArgumentException
<a class="jxr_linenumber" name="151" href="#151">151</a> 	{
<a class="jxr_linenumber" name="152" href="#152">152</a> 		<em class="jxr_comment">// sanity check</em>
<a class="jxr_linenumber" name="153" href="#153">153</a> 		<strong class="jxr_keyword">if</strong> (k &lt; 0)
<a class="jxr_linenumber" name="154" href="#154">154</a> 		{
<a class="jxr_linenumber" name="155" href="#155">155</a> 			<strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException(<span class="jxr_string">"The value of the k parameter cannot be less than zero."</span>);
<a class="jxr_linenumber" name="156" href="#156">156</a> 		}
<a class="jxr_linenumber" name="157" href="#157">157</a> 		<strong class="jxr_keyword">if</strong> (k &gt; n)
<a class="jxr_linenumber" name="158" href="#158">158</a> 		{
<a class="jxr_linenumber" name="159" href="#159">159</a> 			<strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException(<span class="jxr_string">"The value of the k parameter cannot be greater than n, the size of the originalSet."</span>);
<a class="jxr_linenumber" name="160" href="#160">160</a> 		}
<a class="jxr_linenumber" name="161" href="#161">161</a> 
<a class="jxr_linenumber" name="162" href="#162">162</a> 		<em class="jxr_comment">// The end result will be equal to n! / (k! * ((n-k)!))</em>
<a class="jxr_linenumber" name="163" href="#163">163</a> 		
<a class="jxr_linenumber" name="164" href="#164">164</a> 		<em class="jxr_comment">// start by doing some up front evaluation of the denominator</em>
<a class="jxr_linenumber" name="165" href="#165">165</a> 		<strong class="jxr_keyword">int</strong> maxDenomArg;
<a class="jxr_linenumber" name="166" href="#166">166</a> 		<strong class="jxr_keyword">int</strong> minDenomArg;
<a class="jxr_linenumber" name="167" href="#167">167</a> 		<strong class="jxr_keyword">if</strong> ((n-k) &gt; k) {
<a class="jxr_linenumber" name="168" href="#168">168</a> 			maxDenomArg = (n-k);
<a class="jxr_linenumber" name="169" href="#169">169</a> 			minDenomArg = k;
<a class="jxr_linenumber" name="170" href="#170">170</a> 		}
<a class="jxr_linenumber" name="171" href="#171">171</a> 		<strong class="jxr_keyword">else</strong> {
<a class="jxr_linenumber" name="172" href="#172">172</a> 			maxDenomArg = k;
<a class="jxr_linenumber" name="173" href="#173">173</a> 			minDenomArg = (n-k);
<a class="jxr_linenumber" name="174" href="#174">174</a> 		}
<a class="jxr_linenumber" name="175" href="#175">175</a> 		
<a class="jxr_linenumber" name="176" href="#176">176</a> 		<em class="jxr_comment">// First, do an efficient calculation of n! / maxDenomArg!</em>
<a class="jxr_linenumber" name="177" href="#177">177</a> 		BigInteger partialCalculation = BigInteger.ONE;
<a class="jxr_linenumber" name="178" href="#178">178</a> 		<strong class="jxr_keyword">for</strong> (<strong class="jxr_keyword">int</strong> i = maxDenomArg + 1; i &lt;= n; i++) {
<a class="jxr_linenumber" name="179" href="#179">179</a> 			partialCalculation = partialCalculation.multiply(BigInteger.valueOf(i));
<a class="jxr_linenumber" name="180" href="#180">180</a> 		}
<a class="jxr_linenumber" name="181" href="#181">181</a> 		
<a class="jxr_linenumber" name="182" href="#182">182</a> 		<em class="jxr_comment">// Lastly, produce the final solution by calculating partialCalculation / minDenomArg!</em>
<a class="jxr_linenumber" name="183" href="#183">183</a> 		<strong class="jxr_keyword">return</strong> partialCalculation.divide(MathUtil.factorial(minDenomArg));
<a class="jxr_linenumber" name="184" href="#184">184</a> 	}
<a class="jxr_linenumber" name="185" href="#185">185</a> 
<a class="jxr_linenumber" name="186" href="#186">186</a> 	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="187" href="#187">187</a> <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="188" href="#188">188</a> <em class="jxr_javadoccomment">	 * @param &lt;T&gt;</em>
<a class="jxr_linenumber" name="189" href="#189">189</a> <em class="jxr_javadoccomment">	 * @param originalSet</em>
<a class="jxr_linenumber" name="190" href="#190">190</a> <em class="jxr_javadoccomment">	 *            The set of original objects from which combinations of size k</em>
<a class="jxr_linenumber" name="191" href="#191">191</a> <em class="jxr_javadoccomment">	 *            will be generated.</em>
<a class="jxr_linenumber" name="192" href="#192">192</a> <em class="jxr_javadoccomment">	 * @param k</em>
<a class="jxr_linenumber" name="193" href="#193">193</a> <em class="jxr_javadoccomment">	 *            The size of combinations to be generated.</em>
<a class="jxr_linenumber" name="194" href="#194">194</a> <em class="jxr_javadoccomment">	 * @return Returns the set of all size k sets (or combinations) that can be</em>
<a class="jxr_linenumber" name="195" href="#195">195</a> <em class="jxr_javadoccomment">	 *         constructed from the originalSet</em>
<a class="jxr_linenumber" name="196" href="#196">196</a> <em class="jxr_javadoccomment">	 * @throws IllegalArgumentException</em>
<a class="jxr_linenumber" name="197" href="#197">197</a> <em class="jxr_javadoccomment">	 *             thrown if k is less than zero of greater than the size of the</em>
<a class="jxr_linenumber" name="198" href="#198">198</a> <em class="jxr_javadoccomment">	 *             original set.</em>
<a class="jxr_linenumber" name="199" href="#199">199</a> <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="200" href="#200">200</a> 	@SuppressWarnings(<span class="jxr_string">"unchecked"</span>)
<a class="jxr_linenumber" name="201" href="#201">201</a> 	<strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">static</strong> &lt;T&gt; Set&lt;Set&lt;T&gt;&gt; getCombinations(Set&lt;T&gt; originalSet, <strong class="jxr_keyword">int</strong> k) <strong class="jxr_keyword">throws</strong> IllegalArgumentException
<a class="jxr_linenumber" name="202" href="#202">202</a> 	{
<a class="jxr_linenumber" name="203" href="#203">203</a> 
<a class="jxr_linenumber" name="204" href="#204">204</a> 		<em class="jxr_comment">// sanity check</em>
<a class="jxr_linenumber" name="205" href="#205">205</a> 		<strong class="jxr_keyword">if</strong> (k &lt; 0)
<a class="jxr_linenumber" name="206" href="#206">206</a> 		{
<a class="jxr_linenumber" name="207" href="#207">207</a> 			<strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException(<span class="jxr_string">"The value of the k parameter cannot be less than zero."</span>);
<a class="jxr_linenumber" name="208" href="#208">208</a> 		}
<a class="jxr_linenumber" name="209" href="#209">209</a> 		<strong class="jxr_keyword">if</strong> (k &gt; originalSet.size())
<a class="jxr_linenumber" name="210" href="#210">210</a> 		{
<a class="jxr_linenumber" name="211" href="#211">211</a> 			<strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException(<span class="jxr_string">"The value of the k parameter cannot be greater than the size of originalSet."</span>);
<a class="jxr_linenumber" name="212" href="#212">212</a> 		}
<a class="jxr_linenumber" name="213" href="#213">213</a> 
<a class="jxr_linenumber" name="214" href="#214">214</a> 		<em class="jxr_comment">// base case ... k == 0</em>
<a class="jxr_linenumber" name="215" href="#215">215</a> 		<strong class="jxr_keyword">if</strong> (k == 0)
<a class="jxr_linenumber" name="216" href="#216">216</a> 		{
<a class="jxr_linenumber" name="217" href="#217">217</a> 			Set&lt;Set&lt;T&gt;&gt; combinations = <strong class="jxr_keyword">new</strong> HashSet&lt;Set&lt;T&gt;&gt;();
<a class="jxr_linenumber" name="218" href="#218">218</a> 			combinations.add(<strong class="jxr_keyword">new</strong> HashSet&lt;T&gt;());
<a class="jxr_linenumber" name="219" href="#219">219</a> 			<strong class="jxr_keyword">return</strong> combinations;
<a class="jxr_linenumber" name="220" href="#220">220</a> 		}
<a class="jxr_linenumber" name="221" href="#221">221</a> 
<a class="jxr_linenumber" name="222" href="#222">222</a> 		<em class="jxr_comment">// base case ... k == 1</em>
<a class="jxr_linenumber" name="223" href="#223">223</a> 		<strong class="jxr_keyword">if</strong> (k == 1)
<a class="jxr_linenumber" name="224" href="#224">224</a> 		{
<a class="jxr_linenumber" name="225" href="#225">225</a> 			Set&lt;Set&lt;T&gt;&gt; combinations = <strong class="jxr_keyword">new</strong> HashSet&lt;Set&lt;T&gt;&gt;();
<a class="jxr_linenumber" name="226" href="#226">226</a> 			<strong class="jxr_keyword">for</strong> (T t : originalSet)
<a class="jxr_linenumber" name="227" href="#227">227</a> 			{
<a class="jxr_linenumber" name="228" href="#228">228</a> 				Set&lt;T&gt; combination = <strong class="jxr_keyword">new</strong> HashSet&lt;T&gt;();
<a class="jxr_linenumber" name="229" href="#229">229</a> 				combination.add(t);
<a class="jxr_linenumber" name="230" href="#230">230</a> 				combinations.add(combination);
<a class="jxr_linenumber" name="231" href="#231">231</a> 			}
<a class="jxr_linenumber" name="232" href="#232">232</a> 			<strong class="jxr_keyword">return</strong> combinations;
<a class="jxr_linenumber" name="233" href="#233">233</a> 		}
<a class="jxr_linenumber" name="234" href="#234">234</a> 
<a class="jxr_linenumber" name="235" href="#235">235</a> 		<em class="jxr_comment">// recursive case</em>
<a class="jxr_linenumber" name="236" href="#236">236</a> 		T arbitraryElement = (T) CollectionUtils.get(originalSet, 0);
<a class="jxr_linenumber" name="237" href="#237">237</a> 
<a class="jxr_linenumber" name="238" href="#238">238</a> 		Set&lt;T&gt; everythingElse = <strong class="jxr_keyword">new</strong> HashSet&lt;T&gt;(originalSet);
<a class="jxr_linenumber" name="239" href="#239">239</a> 		everythingElse.remove(arbitraryElement);
<a class="jxr_linenumber" name="240" href="#240">240</a> 
<a class="jxr_linenumber" name="241" href="#241">241</a> 		Set&lt;Set&lt;T&gt;&gt; combinations = <strong class="jxr_keyword">new</strong> HashSet&lt;Set&lt;T&gt;&gt;();
<a class="jxr_linenumber" name="242" href="#242">242</a> 
<a class="jxr_linenumber" name="243" href="#243">243</a> 		<em class="jxr_comment">// pair arbitraryElelement with combinations of size k-1 from the</em>
<a class="jxr_linenumber" name="244" href="#244">244</a> 		<em class="jxr_comment">// everythingElse collection</em>
<a class="jxr_linenumber" name="245" href="#245">245</a> 		<strong class="jxr_keyword">for</strong> (Set&lt;T&gt; combinationForEverythingElse : getCombinations(everythingElse, k - 1))
<a class="jxr_linenumber" name="246" href="#246">246</a> 		{
<a class="jxr_linenumber" name="247" href="#247">247</a> 			combinationForEverythingElse.add(arbitraryElement);
<a class="jxr_linenumber" name="248" href="#248">248</a> 			combinations.add(combinationForEverythingElse);
<a class="jxr_linenumber" name="249" href="#249">249</a> 		}
<a class="jxr_linenumber" name="250" href="#250">250</a> 
<a class="jxr_linenumber" name="251" href="#251">251</a> 		<em class="jxr_comment">// get combinations of size k from the everythingElse collection</em>
<a class="jxr_linenumber" name="252" href="#252">252</a> 		<strong class="jxr_keyword">if</strong> (k &lt;= everythingElse.size())
<a class="jxr_linenumber" name="253" href="#253">253</a> 		{
<a class="jxr_linenumber" name="254" href="#254">254</a> 			<strong class="jxr_keyword">for</strong> (Set&lt;T&gt; combinationForEverythingElse : getCombinations(everythingElse, k))
<a class="jxr_linenumber" name="255" href="#255">255</a> 			{
<a class="jxr_linenumber" name="256" href="#256">256</a> 				combinations.add(combinationForEverythingElse);
<a class="jxr_linenumber" name="257" href="#257">257</a> 			}
<a class="jxr_linenumber" name="258" href="#258">258</a> 		}
<a class="jxr_linenumber" name="259" href="#259">259</a> 
<a class="jxr_linenumber" name="260" href="#260">260</a> 		<strong class="jxr_keyword">return</strong> combinations;
<a class="jxr_linenumber" name="261" href="#261">261</a> 	}
<a class="jxr_linenumber" name="262" href="#262">262</a> 
<a class="jxr_linenumber" name="263" href="#263">263</a> 	<em class="jxr_javadoccomment">/**</em>
<a class="jxr_linenumber" name="264" href="#264">264</a> <em class="jxr_javadoccomment">	 * </em>
<a class="jxr_linenumber" name="265" href="#265">265</a> <em class="jxr_javadoccomment">	 * @param &lt;T&gt;</em>
<a class="jxr_linenumber" name="266" href="#266">266</a> <em class="jxr_javadoccomment">	 * @param originals</em>
<a class="jxr_linenumber" name="267" href="#267">267</a> <em class="jxr_javadoccomment">	 * @param pageSize</em>
<a class="jxr_linenumber" name="268" href="#268">268</a> <em class="jxr_javadoccomment">	 * @return Returns one or more pages containing at most pageSize original</em>
<a class="jxr_linenumber" name="269" href="#269">269</a> <em class="jxr_javadoccomment">	 *         objects.</em>
<a class="jxr_linenumber" name="270" href="#270">270</a> <em class="jxr_javadoccomment">	 * @throws IllegalArgumentException</em>
<a class="jxr_linenumber" name="271" href="#271">271</a> <em class="jxr_javadoccomment">	 *             Thrown if the originals parameter is null or if the</em>
<a class="jxr_linenumber" name="272" href="#272">272</a> <em class="jxr_javadoccomment">	 *             pageSizeParameter is less than one.</em>
<a class="jxr_linenumber" name="273" href="#273">273</a> <em class="jxr_javadoccomment">	 */</em>
<a class="jxr_linenumber" name="274" href="#274">274</a> 	<strong class="jxr_keyword">public</strong> <strong class="jxr_keyword">static</strong> &lt;T&gt; List&lt;List&lt;T&gt;&gt; page(Collection&lt;T&gt; originals, <strong class="jxr_keyword">int</strong> pageSize) <strong class="jxr_keyword">throws</strong> IllegalArgumentException
<a class="jxr_linenumber" name="275" href="#275">275</a> 	{
<a class="jxr_linenumber" name="276" href="#276">276</a> 
<a class="jxr_linenumber" name="277" href="#277">277</a> 		<strong class="jxr_keyword">if</strong> (originals == <strong class="jxr_keyword">null</strong>)
<a class="jxr_linenumber" name="278" href="#278">278</a> 		{
<a class="jxr_linenumber" name="279" href="#279">279</a> 			<strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException(<span class="jxr_string">"Cannot page a null collection or originals."</span>);
<a class="jxr_linenumber" name="280" href="#280">280</a> 		}
<a class="jxr_linenumber" name="281" href="#281">281</a> 		<strong class="jxr_keyword">if</strong> (pageSize &lt; 1)
<a class="jxr_linenumber" name="282" href="#282">282</a> 		{
<a class="jxr_linenumber" name="283" href="#283">283</a> 			<strong class="jxr_keyword">throw</strong> <strong class="jxr_keyword">new</strong> IllegalArgumentException(<span class="jxr_string">"The pageSize argument must be greater than or equal to one."</span>);
<a class="jxr_linenumber" name="284" href="#284">284</a> 		}
<a class="jxr_linenumber" name="285" href="#285">285</a> 
<a class="jxr_linenumber" name="286" href="#286">286</a> 		List&lt;List&lt;T&gt;&gt; pages = <strong class="jxr_keyword">new</strong> ArrayList&lt;List&lt;T&gt;&gt;();
<a class="jxr_linenumber" name="287" href="#287">287</a> 
<a class="jxr_linenumber" name="288" href="#288">288</a> 		List&lt;T&gt; currentPage = <strong class="jxr_keyword">null</strong>;
<a class="jxr_linenumber" name="289" href="#289">289</a> 
<a class="jxr_linenumber" name="290" href="#290">290</a> 		<strong class="jxr_keyword">for</strong> (T original : originals)
<a class="jxr_linenumber" name="291" href="#291">291</a> 		{
<a class="jxr_linenumber" name="292" href="#292">292</a> 
<a class="jxr_linenumber" name="293" href="#293">293</a> 			<strong class="jxr_keyword">if</strong> (currentPage == <strong class="jxr_keyword">null</strong> || currentPage.size() == pageSize)
<a class="jxr_linenumber" name="294" href="#294">294</a> 			{
<a class="jxr_linenumber" name="295" href="#295">295</a> 				currentPage = <strong class="jxr_keyword">new</strong> ArrayList&lt;T&gt;();
<a class="jxr_linenumber" name="296" href="#296">296</a> 				pages.add(currentPage);
<a class="jxr_linenumber" name="297" href="#297">297</a> 			}
<a class="jxr_linenumber" name="298" href="#298">298</a> 
<a class="jxr_linenumber" name="299" href="#299">299</a> 			currentPage.add(original);
<a class="jxr_linenumber" name="300" href="#300">300</a> 
<a class="jxr_linenumber" name="301" href="#301">301</a> 		}
<a class="jxr_linenumber" name="302" href="#302">302</a> 
<a class="jxr_linenumber" name="303" href="#303">303</a> 		<strong class="jxr_keyword">return</strong> pages;
<a class="jxr_linenumber" name="304" href="#304">304</a> 
<a class="jxr_linenumber" name="305" href="#305">305</a> 	}
<a class="jxr_linenumber" name="306" href="#306">306</a> 
<a class="jxr_linenumber" name="307" href="#307">307</a> }
</pre>
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